I'm wondering if the Wii U will incorporate something like the xbox live where you can play older multiplayer games online. For example, multiplayer games like Contra 3, super mario world, Super mario kart and zombies ate my neighbors. This sounds a bit hard to do maybe, but its something thats always excited me in a more social nintendo system, something the Wii U seems to kinda try to do.

I mean, the xbox lets you gives you the ability to play sega genesis games online like gunstar heroes, its gotta be doable, with Wii U's hardware is the real question, however. True wii didnt do it, but that was when nintendo was saying people didnt want to play online with others and wii u and 3ds is supposedly more "social".

The main problem with retro multiplayer gaming through multiple units is sync issues. Unlike multiplayer games nowadays, which deal with each client sending data to the server/host, and the host processing the data and sending the relevant data back to them all, retro systems had multiplayer enclosed in a single unit. There was no host/client implementation. It was just Player 1, Player 2, etc that all used the same CPU, RAM, etc. That means, to think of it in one way, each player had an exact copy of all the data that was being processed immediately. Multiplayer games nowadays do not have exact copies of their connected associates, but approximations, and to throw that approximation into the retro scenario would be chaos.

The current method for retro multiplayer syncing is to give each client an entire copy of the host's memory for the program at set intervals, and for the time in between have everyone, both client and host, send their button presses to each other, so that each person's device processes the information individually. The more often an exact copy is sent out, the more "in-sync" the devices will be. Any latency added will throw off the processing, and the game will be shown as "jumping" when an exact copy of the memory gets sent. The only person that will not be shown as jumpy is the host, which everyone else is basing their processing on, but that "Player 1" will notice that his friends may operate a little differently because they are continually having to operate with re-syncing.

To put into perspective of just how much online speed is required, let's use the SNES as an example. The SNES has 128kBytes of RAM (not including VRAM, audio RAM, etc, but let's ignore those for the moment). In order to have all the systems in sync without skipping a frame out of the 60fps NTSC available (50fps for PAL), that comes to about 7.68MB/s (6.4MB/s for PAL) that needs to be synced with the clients, granted no latency gets in the way (which is impossible right now). Reduce that to sending a copy every 3 frames instead of every frame transfer (to 20fps NTSC), and the transfer rate required drops to 2.56MB/s, but doesn't include the per bytes per frame in between for button presses.